This project is an investigation of the role of the nervous system on the regulation of insulin release. The pancreatic islets of the teleost fish, Gillichthys mirabilis, have been chosen for study because of their large size and elaborate innervation of the islet cells. The extent and nature of the innervation will be investigated by iontophoresis of cobaltous chloride and by electron microscopy. The role of the nervous system upon insulin release will be studied by incubating islets in vitro in the presence of various neurotransmitter substances, followed by radioimmunoassay of the incubation media. Islets will also be transplanted sublingually and will subsequently be incubated in vitro in order to assess the effects of a lack of a nervous supply upon insulin release.